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Terminal Velocity

  1. Nov 11, 2007 #1
    A 1.5-mm-diameter steel ball bearing (7830 kg/m^3) is dropped into a tank of SAE 30 oil. What is its terminal velocity?

    The density of oil is 917kg/m^3, and the viscosity of oil is 0.26kg/(m*s).

    Help is much appreciated!
  2. jcsd
  3. Nov 11, 2007 #2
    What have you tried so far?

    Where are you stuck?
  4. Nov 11, 2007 #3
    Force of drag = 1/2 * (density of fluid) * (area of sphere) * v^2 * (coefficient of drag)
    Force of drag = 3 * pi * (coefficient of fluid) * (diameter of obj) * v

    Coefficient of drag = 24 / (Reynolds number)

    Reynolds number = (density of fluid * velocity of fluid * chracteristic length)/(viscosity of fluid)

    When I combine the equations, v cancels out so I cannot solve for it. Is there another equation I should be using?
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